The present invention relates generally to turbine buckets and, more particularly, to a method and system for estimating turbine bucket condition and remaining service life using pyrometer signals as primary input.
Buckets are critical gas turbine components. Unexpected failures of buckets almost always result in high maintenance costs. Typically, potential failures are not directly measurable during turbine operation. The current analytical approach in estimating bucket life due to oxidation requires accurate measurement of absolute bucket metal temperature. However, measurement of accurate xe2x80x9cabsolutexe2x80x9d temperature is not trivial due to many uncertainties including environmental effects, sensor degradation, etc. In addition, this analytical approach cannot detect the presence of defects (oxidation), so there is difficulty in estimating remaining useful life of the bucket.
Optical pyrometers have been used to measure temperature of metal surfaces. Optical pyrometers provide many advantages in determining the spatial and time varying temperature distribution of fast rotating components in gas turbines. Their capability is considered to be limited to the xe2x80x9cline of sight (LOS) xe2x80x9d which is the optical path of a turbine pyrometer, since the pyrometer measures the temperature only along a small target spot (commonly 1 mm-26 mm).
Previous studies have described the application of a high resolution turbine pyrometer to heavy duty gas turbines, compared the capability of long wavelength infrared pyrometers with short infrared wavelengths, and described the development and evaluation of a versatile high resolution pyrometer system and its application to radial turbine rotor temperature mapping. None of these studies, however, attempts to assess the condition of the bucket using the pyrometer signal.
Researchers have developed a number of diagnostic algorithms and applied them to vibration sensors, such as accelerometers for machinery health monitoring. There is difficulty, however, in detecting the defect (oxidation) using such vibration sensors. Furthermore, none of the researchers has attempted to apply diagnostic techniques to optical sensors, such as pyrometers, for bucket health monitoring.
In an exemplary embodiment of the invention, a method of estimating turbine bucket oxidation condition includes (a) measuring, with a pyrometer, time-varying temperature distributions of at least one rotating turbine bucket; and (b) determining a condition index based on the measured time-varying temperature distributions, the condition index reflecting at least one of an overall condition of a bucket set or a specific condition of a single bucket.
In another exemplary embodiment, a method is provided for estimating turbine bucket oxidation condition and predicting remaining useful bucket life during operation of a turbine by processing time-varying temperature distributions measured with a pyrometer of at least one rotating turbine bucket.
In still another exemplary embodiment of the invention, a system for estimating turbine bucket oxidation condition includes a pyrometer that measures time-varying temperature distributions of at least one rotating turbine bucket; and a processor receiving output from the pyrometer. The processor determines a condition index based on the measured time-varying temperature distributions, which condition index reflects at least one of an overall condition of a bucket set or a specific condition of a single bucket.